The anti-D immunoglobulin neutralises any RhD positive antigens that may have entered the mother's blood during pregnancy. If the antigens have been neutralised, the mother's blood won't produce antibodies.
You'll be offered anti-D immunoglobulin if it's thought there's a risk that RhD antigens from your baby have entered your blood – for example, if you experience any bleeding, if you have an invasive procedure (such as amniocentesis), or if you experience any abdominal injury.
Anti-D immunoglobulin is also administered routinely during the third trimester of your pregnancy if your blood type is RhD negative. This is because it's likely that small amounts of blood from your baby will pass into your blood during this time.
This routine administration of anti-D immunoglobulin is called routine antenatal anti-D prophylaxis, or RAADP (prophylaxis means a step taken to prevent something from happening).
Routine antenatal anti-D prophylaxis (RAADP)
There are currently two ways you can receive RAADP:
- a 1-dose treatment: where you receive an injection of immunoglobulin at some point during weeks 28 to 30 of your pregnancy
- a 2-dose treatment: where you receive 2 injections; one during the 28th week and the other during the 34th week of your pregnancy
There doesn't seem to be any difference in the effectiveness between the 1-dose or 2-dose treatments. Your local clinical commissioning group (CCG) may prefer to use a 1-dose treatment, because it can be more efficient in terms of resources and time.
When will RAADP be given?
RAADP is recommended for all pregnant RhD negative women who haven't been sensitised to the RhD antigen, even if you previously had an injection of anti-D immunoglobulin.
As RAADP doesn't offer lifelong protection against rhesus disease, it will be offered every time you become pregnant if you meet these criteria.
RAADP won't work if you've already been sensitised. In these cases, you'll be closely monitored so treatment can begin as soon as possible if problems develop.
Anti-D immunoglobulin after birth
After giving birth, a sample of your baby's blood will be taken from the umbilical cord. If you're RhD negative and your baby is RhD positive, and you haven't already been sensitised, you'll be offered an injection of anti-D immunoglobulin within 72 hours of giving birth.
The injection will destroy any RhD positive blood cells that may have crossed over into your bloodstream during the delivery. This means your blood won't have a chance to produce antibodies and will significantly decrease the risk of your next baby having rhesus disease.
Complications from anti-D immunoglobulin
Although the anti-D immunoglobulin, which is made from donor plasma, will be carefully screened, there's a very small risk that an infection could be transferred through the injection.
However, the evidence in support of RAADP shows that the benefits of preventing sensitisation far outweigh these small risks.